A coupling for connecting a reamer to a driving motor is described in U.S. Pat. No. 5,720,749. That reamer is used in particular to enlarge the medullary canals of bone and comprises essentially a cutting head detachably connectable to a flexible shaft linked to a source of rotational drive power. The elements of the coupling comprise, on the side of the cutting tool, a hollow tubular coupling shank and, on the side of the flexible shaft, a male connector insertable into the bore of said coupling shank. Both the hollow coupling shank and the male connector have essentially the form of a hollow cylindrical body, the outer lateral area of the male connector and the inner lateral area of the hollow coupling shank each having two parallel surfaces which correspond to each other and extend over a part of their lengths. On the male connector, these surfaces terminate short of the front end facing the coupling, so as to define two latch fingers on this end of the male connector. In addition, the wall of the male connector is provided with axial slots so as to define flexible arms. As the male connector is inserted into the hollow coupling shank, the two arms equipped with latch fingers are radially compressed until the male connector is completely inserted and the latch fingers engage with corresponding peripheral slots formed in the wall of the hollow coupling shank. Thus the male connector is rotationally and axially held in a fixed position within the hollow coupling shank. In order to remove the cutting head, the flexible arms of the male connector are compressed from outside of the hollow coupling shank by a compressive force applied through the peripheral slots thereof, so that the latch fingers disengage from these slots and the male connector can be pulled out of the hollow coupling shank. A disadvantage of this known apparatus consists in the necessity to have a special device for compressing the flexible arms from outside through the peripheral slots in order to be able to remove the cutting head. In addition, the connection between shaft and male connector is realized as a press-fitted engagement, which implies the disadvantage that a guide wire or Kirschner wire which may be inserted in the bore of the male connector can only be rotated with considerable friction loss.
A need exists for a coupling device to remedy these drawbacks and provide a coupling which allows the interconnectable parts to be joined together and removed without the aid of auxiliary instruments or devices. In addition, a need exists for a coupling that is made in such a way that when the parts are joined together, they will be firmly held against axial or rotational displacement in both directions.